A Nearly Naked Supermassive Black Hole

TL;DR

This paper reports the discovery of a nearly naked supermassive black hole, ejected from its host galaxy after tidal disruption, characterized by its bright radio emission and high velocity, providing insights into black hole dynamics.

Contribution

It presents the first observational evidence of a supermassive black hole ejected from a galaxy due to tidal interactions, with detailed analysis of its properties and environment.

Findings

Identified a supermassive black hole offset from its host galaxy

Detected high velocity and tidal debris indicating ejection

Measured properties consistent with a nearly naked SMBH

Abstract

During a systematic search for supermassive black holes (SMBHs) not in galactic nuclei, we identified the compact symmetric radio source B3 1715+425 with an emission-line galaxy offset ~ 8.5 kpc from the nucleus of the brightest cluster galaxy (BCG) in the redshift $z = 0.1754$ cluster ZwCl 8193. B3 1715+425 is too bright (brightness temperature $\sim 3 \times 10^{10}$ K at observing frequency 7.6 GHz) and too luminous (1.4 GHz luminosity $\sim 10^{25}$ W/Hz) to be powered by anything but a SMBH, but its host galaxy is much smaller ($\sim 0.9$ kpc $\times$ 0.6 kpc full width between half-maximum points) and optically fainter (R-band absolute magnitude $\sim -18.2$) than any other radio galaxy. Its high radial velocity $\sim 1860$ km/s relative to the BCG, continuous ionized wake extending back to the BCG nucleus, and surrounding debris indicate that the radio galaxy was tidally shredded passing through the BCG core, leaving a nearly naked supermassive black hole fleeing from the BCG with space velocity $> 2000$ km/s. The radio galaxy has mass $< 6 \times 10^9$ solar masses and infrared luminosity $\sim 3 \times 10^{11}$ solar luminosities close to its dust Eddington limit, so it is vulnerable to further mass loss from radiative feedback.